1,354,446 research outputs found
New routes in polyoxometalate chemistry : from keplerates to chemistry under confined conditions
No full textTodea AM. New routes in polyoxometalate chemistry : from keplerates to chemistry under confined conditions. Bielefeld (Germany): Bielefeld University; 2008
A silicified Todea trunk (Osmundaceae) from the Eocene of Patagonia
No full textThe Osmundaceae family is the sister group to all other extant leptosporangiate ferns. Its rich fossil record has enabled detailed reconstructions of the evolutionary history of the group. Fossil evidence for today’s Southern Hemisphere subtribe Todeinae, however, has been difcult to accumulate, with only two unambiguous fossil occurrences of modern Todea. Here, we describe a silicifed Todea stem from the Eocene Laguna del Hunco lagerstätte of Patagonia. The stem contains a heterogeneous outer cortex with distinct fbrous rings surrounding the leaf traces, indicative of subtribe Todeinae; nests of thick-walled fbres associated with departing leaf traces together with the sclerenchymatous pith and with abundant sclerenchyma fbres in the inner stipe cortex enable assignment to Todea. The stem difers from T. tidwellii—the only other known fossil Todea stem described thus far—mainly in lacking sclerenchyma lining the adaxial concavity of the stipe bundle. Co-occurrence with sterile foliage fragments indicates that the stem may belong to Todea amissa, a species that was initially described based on frond compressions from the same deposits. Our fnding corroborates the widely disjunct Gondwanan distribution of Todea across the Southern Hemisphere in the past, and provides an impetus to re-assess genetic divergence between the relictual African and Australasian populations of Todea barbara today in order to resolve the evolutionary history of the group more clearly. Finally, this frst report of structurally preserved plant remains from Laguna del Hunco highlights the thus far untapped potential for anatomical preservation in this important fossil lagerstätte.Fil: Bomfleur, Benjamin. Westfälische Wilhelms Universität; AlemaniaFil: Escapa, Ignacio Hernán. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Todea from the Lower Cretaceous of western North America: implications for the phylogeny, systematics, and evolution of modern Osmundaceae
No full textThe first fossil evidence for the fern genus Todea has been recovered from the Lower Cretaceous of British Columbia, Canada, providing paleontological data to strengthen hypotheses regarding patterns of evolution and phylogeny within Osmundaceae. The fossil consists of a branching rhizome, adventitious roots, and leaf bases. The dictyoxylic stem has up to eight xylem bundles around a sclerenchymatous pith. Leaf traces diverge from cauline bundles in a typical osmundaceous pattern and leaf bases display a sheath of sclerenchyma around a C-shaped xylem trace with 2 – 8 protoxylem strands. Within the adaxial concavity of each leaf trace, a single sclerenchyma bundle becomes C-shaped as it enters the cortex. The sclerotic cortex is heterogeneous with an indistinct outer margin. The discovery of Todea tidwellii sp. nov. reveals that the genus Todea evolved by the Lower Cretaceous. A phylogenetic analysis combining morphological characters of living and extinct species with a previously published nucleotide sequence matrix confirms the taxonomic placement of T. tidwellii . Results also support the hypothesis that Osmunda s.l. represents a paraphyletic assemblage and that living species be segregated into two genera, Osmunda and Osmundastrum . Fossil evidence confirms that Osmundaceae originated in the Southern Hemisphere during the Permian, underwent rapid diversification, and species extended around the world during the Triassic. Crown group Osmundaceae originated by the Late Triassic, with living species appearing by the Late Cretaceous
Todea Willd. ex Bernh., J. Bot. (Schrader
No full text8.3. Todea Willd. ex Bernh., J. Bot. (Schrader) 1800(2): 126 (1801). T.: Todea africana Willd. ex Bernh, nom. illeg. = T. barbara (L.) T.MoorePublished as part of Christenhusz, Maarten J. M., Zhang, Xian-Chun & Schneider, Harald, 2011, A linear sequence of extant families and genera of lycophytes and ferns, pp. 7-54 in Phytotaxa 19 on page 42, DOI: 10.11646/phytotaxa.19.1.2, http://zenodo.org/record/489399
Palaeoxylotomical Study Of A New Collection From Zarand Miocene Petrified Forest, South Apuseni Mts.
No full textIamandei, Stanila, Iamandei, Eugenia, Todea, Petru (2020): Palaeoxylotomical Study Of A New Collection From Zarand Miocene Petrified Forest, South Apuseni Mts. Acta Palaeontologica Romaniae 16 (1): 19-34, DOI: 10.35463/j.apr.2020.01.02, URL: http://dx.doi.org/10.35463/j.apr.2020.01.0
Criteria for Engineering Cutinases: Bioinformatics Analysis of Catalophores
No full textCutinases are bacterial and fungal enzymes that catalyze the hydrolysis of natural cutin,
a three-dimensional inter-esterified polyester with epoxy-hydroxy fatty acids with chain lengths
between 16 and 18 carbon atoms. Due to their ability to accept long chain substrates, cutinases are also
effective in catalyzing in vitro both the degradation and synthesis of several synthetic polyesters and
polyamides. Here, we present a bioinformatics study that intends to correlate the structural features
of cutinases with their catalytic properties to provide rational basis for their effective exploitation,
particularly in polymer synthesis and biodegradation. The bioinformatics study used the BioGPS
method (Global Positioning System in Biological Space) that computed molecular descriptors based
on Molecular Interaction Fields (MIFs) described in the GRID force field. The information was
used to generate catalophores, spatial representations of the ability of each enzymatic active site
to establish hydrophobic and electrostatic interactions. These tools were exploited for comparing
cutinases to other serine-hydrolases enzymes, namely lipases, esterases, amidases and proteases,
and for highlighting differences and similarities that might guide rational engineering strategies.
Structural features of cutinases with their catalytic properties were correlated. The “catalophore” of
cutinases indicate shared features with lipases and esterases
Complete chloroplast genome of Austral king fern Todea barbara (L.) Moore (Osmundaceae)
No full textIn this study, we determined the chloroplast genome sequence of the Austral king fern, Todea barbara (L.) Moore. The plastome of T. barbara is a typical circular form composed of 144,208 bp with two inverted repeats (IRs; 10,442 bp), a large single copy (LSC; 101,059 bp), and a small single copy (SSC; 22,265 bp). The complete sequence comprises 131 genes, namely 85 protein-coding genes, eight ribosomal RNAs, and 38 transfer RNAs. The guanine–cytosine (GC) content of the genome was found to be 39.9%. Additionally, U-to-C RNA editing sites were identified in eight genes: atpE, chlB, clpP, matK, rpl20, rpoB, rpoC1, and rpoC2. Phylogenetic analysis using 85 coding gene sequences revealed that the genera Todea and Osmunda form a clade and that the genus Osmundastrum is a sister genus to both
First record of Todea (Osmundaceae) in South America, from the early Eocene paleorainforests of Laguna del Hunco (Patagonia, Argentina)
No full textPremise of the Study: The early Eocene Laguna del Hunco caldera-lake paleoflora (ca. 52 Ma) from Chubut Province, Argentina, is notably diverse and includes many conifer and angiosperm lineages that are extinct in South America but extant in Australasian rainforests. No ferns have been previously described from Laguna del Hunco. We describe and interpret a new species of fossil Osmundaceae based on fertile and sterile pinnae.
Methods: The fossil specimens were compared with other extant and fossil Osmundaceae based on living and herbarium material and published descriptions. A morphological matrix based on 29 characters was constructed for 17 living species in Osmundaceae, four species assigned to the fossil genus Todites, and the new fossil species. Phylogenetic analyses were conducted under parsimony using morphology and total evidence matrices.
Key Results: Both the new fossil and the Todites species were consistently resolved within the leptopteroid clade of Osmundaceae, and the new species resolved in a clade with the two living Todea species, which are now restricted to Australia, New Guinea, New Zealand, and southern Africa.
Conclusions: Todea amissa sp. nov. is the first record of Todea, living or fossil, in South America and only the second fossil record worldwide. The distribution of extant Todea on Gondwanan continents other than South America is broadly shared with other taxa from Laguna del Hunco, further indicating that a large component of this flora represents a Gondwanic biome that is no longer found on the South American continent.Fil: Carvalho, Monica. Cornell University; Estados Unidos. State University Of Pennsylvania; Estados UnidosFil: Wilf, Peter. State University Of Pennsylvania; Estados UnidosFil: Hermsen, Elizabeth. Ohio University; Estados UnidosFil: Gandolfo, Maria. Cornell University; Estados UnidosFil: Cuneo, Nestor Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Johnson, Kirk. National Museum of Natural History; Estados Unido
Softening of Pore and Interior Properties of a Metal-Oxide-Based Capsule: Substituting 60 Oxide by 60 Sulfide Ligands
No full textSchäffer C, Todea AM, Bögge H, et al. Softening of Pore and Interior Properties of a Metal-Oxide-Based Capsule: Substituting 60 Oxide by 60 Sulfide Ligands. Angewandte Chemie International Edition. 2011;50(51):12326-12329
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
